Fatigue Life Analysis Of Interface Between The Aircraft Hatch Truss And Skin

The aircraft truss and skin are mainly screw joint,co curing and joint joint.Because of the excellent bonding performance of the joint interface and co curing interface,it becomes an important connection mode of composite materials.Because of the large difference in physical properties between the adhesive and the bonding laminate,and the complex damage behavior of the interface,it is difficult to fully study the damage propagation law and fatigue performance of the interface.The properties of the bonding interface play an important role in the bearing capacity,damage behavior and fatigue resistance of the material and structure.Therefore,it is very important to analyze the damage evolution process and fatigue performance of the interface for accurate evaluation of interface performance and its subsequent design and application.In this paper,the advantages and limitations of cohesive interface model in carbon fiber reinforced composites are studied and analyzed.Based on this,a reasonable scheme is proposed to obtain S-N curve and damage evolution parameters in cohesive interface constitutive model by experiment and finite element simulation;Then,the ultimate bearing capacity,interface damage mode and damage propagation law of different truss skin connection structures under static pull-out loading are studied by static simulation analysis.Then the pull-out fatigue performance and residual strength of different types of test pieces in the design life are analyzed by fatigue test;Finally,the pull-out fatigue life of the structure is obtained by fatigue simulation analysis,which verifies the accuracy and feasibility of the parameter determination scheme proposed in this paper.The results of fatigue simulation and test show that:(1)the fatigue resistance of composite bonded structures is affected by the connection mode and the number of layers of bonded laminates,in which the connection mode plays a leading role,and the co curing connection has better fatigue performance than the co bonding connection;(2)The initial damage of interface will seriously reduce the pull-out fatigue performance of CO bonded or co cured structures;(3)By comparing the fatigue life simulation results with the test results,the reliability of the finite element simulation results is verified.The static tensile simulation results show that:(1)the static tensile properties of composite bonded structures are affected by the connection mode and the number of layers of bonded laminates,in which the connection mode plays a leading role;(2)The cohesive interface element starts to damage from the position where it connects with the filling area(where the stress is the largest),and the damage area gradually expands to both sides until the structure is completely failed;This work has reference significance for the study of fatigue resistance and damage behavior of composite joint interface,and provides a strong theoretical support for the subsequent composite joint design and application.